Effect of Rolling Pass on Porosity Void Closure of Bloom during Hot-Core Heavy Reduction Rolling

Some heavy reduction technologies near the solidification end have been gradually applied to casting slabs or blooms in recent years to eliminate internal shrinkage cavities. These technologies can be roughly classified as single-pass reduction type and multi-pass reduction type. To date, the conclusions about the influence of reduction type on void closure are inconsistent. Herein, based on the simulation experiments, the influence of the reduction type on the closure of the shrinkage cavity in bloom during hot-core heavy reduction rolling (HHR2) was investigated with the physical metallurgical model and numerical simulation. HHR2 processes with single-pass type and double-pass type were designed to evaluate void closure behavior, and the total reduction amount of different reduction types was 60 mm in both cases. Results show that the single-pass reduction type of HHR2 is more beneficial to the closure of the shrinkage cavity in bloom than the double-pass reduction type. Furthermore, the difference between the two reduction types was pointed out, which mainly includes three aspects: the geometry of the deformation zone, inter-pass static recrystallization and temperature of bloom. Finally, a quantitative analysis of the effect of the three abovementioned factors on void closure was performed. The obtained results show that the geometry of the deformation zone is the main factor, which leads to different degrees of void closure in different reduction types.

Automated summary

In recent years, some heavy reduction technologies have been applied to casting slabs or blooms to eliminate internal shrinkage cavities. These technologies can be classified as single-pass reduction type and multi-pass reduction type. However, there is no consistent conclusion about the influence of reduction type on void closure. This study investigated the influence of reduction type on the closure of shrinkage cavity in bloom during hot-core heavy reduction rolling (HHR2) through simulation experiments.